1. Field of the Invention
The present invention relates to a trailer hitch coupling assembly, and more particularly, to a pin box assembly using a combination pin box and extension assembly with locking features to facilitate a change in the axis of rotation of a fifth wheel trailer when attached to a towing vehicle.
2. Description of the Background of the Invention
Fifth wheel trailers have customarily been adapted with a coupling apparatus which facilitates attachment to a towing vehicle. Typically, a standard fifth wheel hitch is mounted on the towing vehicle, where a standard pin box on the fifth wheel trailer is adapted with a king pin to fit the hitch and properly support the weight of the trailer.
The towing vehicle, equipped with the hitch, and with the trailer secured, can then be driven supporting the trailer, which rotates securely around an axis created by the interconnect between the trailer king pin and the adaptive mount on the hitch.
Numerous advancements in the art have been shown. For example, as disclosed in U.S. Pat. No. 6,986,524, a fifth wheel pin box assembly with a rubber shear spring to accomplish appreciable cushioned movement in the connection between the towing vehicle and the trailer.
Another example includes an extension coupling for use with trailers, as described in U.S. Pat. No. 5,890,728, in which a retainer assembly engages the trailer hitch to resist rotation around the king pin axis and force rotation of the trailer back to a separate axis. This coupling was developed to accommodate use on only short-bed towing vehicles where a more forward axis of rotation of the trailer could cause impact between the trailer and the cab of the towing vehicle. Additionally, by design, this coupling introduces uneven stress on a trailer hitch in its engagement when turning maneuvers are instituted.
Many consumers of fifth wheel trailers may own different towing vehicles, including those of the short-bed and long-bed varieties. It would be desirable to have a hitch coupling assembly available for use with a variety of towing vehicles, in which the axis of rotation is easily moved forward or backward based on towing-vehicle bed length through use of a locking mechanism.